Assume the mean useful life of a particular light bulb is 2,000 hours and is normally distributed with a standard deviation of 300 hours. Calculate the useful life of the light bulb within two standard deviations of the mean.
A)Between 1,700 and 2,300 hours
B)Longer than 2,300 hours
C)Longer than 1,700 hours
D)Between 1,400 and 2,600 hours

Question

Quizplus · Accepted Answer

Two standard deviations from the mean in a normal distribution includes values between mean - 2*standard deviation and mean + 2*standard deviation. Here, that's 2000 - 2*300 to 2000 + 2*300, or 1400 to 2600 hours.

Assume the Mean Useful Life of a Particular Light Bulb